1. Field of the Invention
This invention relates generally to position monitoring devices which use inertial principles, such a gyroscopes, and more particularly to an improved, inexpensive apparatus designed to automatically monitor a vehicle's position through the monitoring of attitude changes and accelerations.
2. Description of Related Art
Invention and use of position sensing devices is known to the public, as they are frequently employed to sense and monitor the position of a wide variety of different objects. For example, such devices are frequently employed in mouse or trackball configurations, as seen in Bose U.S. Pat. No. 3,625,083. As disclosed, this device consists of a two-axis digital track ball encoder that has a manually controlled bearing-supported spherical ball which, when rotated, actuates two rotatable encoders frictionally coupled to the ball surface and oriented 90 degrees from each other so that the output of one encoder represents an X function and the other a Y function.
Lawrence et al. U.S. Pat. No. 4,939,508 discloses a point and select device in which a sphere protruding from one major surface of a housing can serve as either a trackball or the moving element in a mouse. Actuators on either side of the device are selected according to the use of the device. The sense of motion for up/down is reversed between the two modes of operation.
Houston U.S. Pat. No. 5,168,221 discloses a pivotal magnetic coupling and position sensor that has two torodial magnets coupled to each other by a ferrous spherical spacer. The spacer partially engages openings provided in the two magnet surfaces facing each other. The facing magnet surfaces have the same polarity so that they repel one another. The configuration creates a stable equilibrium by conduction of the magnetic flux through the spacer and the repulsive forces at the periphery of the magnets. This structure forms a resilient pivot joint at which, when capped by a spherical handle attached to the upper magnet, becomes a multiple-axis pointing device or tactile sensor.
Gyroscopes are another common application for position sensing and monitoring devices, as gyroscopes commonly are employed to keep moving vehicles such as ships, airplanes and missiles on course. There are a wide variety of different types of gyroscopes that are currently in use today. Originally, gyroscopes generally consisted of a heavy, rotating wheel or disk mounted so that its axis could turn freely in one or more directions. More recently, however, fiber optic and ring laser gyroscopes have replaced spinning mass machines.
For example, Martin U.S. Pat. No. 5,371,589 discloses a monolithic triaxial ring laser gyroscope that includes three orthogonal ring cavities, the optical path length of each of which is independently controllable. Three planar ring cavities are formed within a frame that is shaped into the form of a rhombic dodecahedron. A mirror is fixed to each of the twelve faces of the frame for directing the counter propagating light beams within the three orthogonal cavities. Anodes which communicate with the cavities through bore holes are fixed to predetermined surfaces of the frame while three cathodes are positioned at flattened portions of preselected vertices of the dodecahedron and located in such a way as to eliminate undesired bias. Martin et al. U.S. Pat. No. 5,371,591 discloses a somewhat similar multioscillator.
The types of instruments described above are complex precision machines having high original cost of procurement, high cost of operation, and significant cost of personnel training and so on. In addition, the present instrument for monitoring position change, tilt, accelerations, etc. are not generally of very high precision, so that they are not applicable to applications requiring low precision, ease of use and simplicity of operation. The present invention fulfills these needs and provides further related advantages as described in the following summary.